Why won't Rigify deform my High Poly Mesh?
It's hard to tell what's going wrong if you provide only your mesh without the rig you did.

But certainly, you can't do animation with a raw mesh of 2 billion triangles. It's just unmanageable. Performances will be below ground level, you wont be able to have correct control over the weights and deformations, ...

The common workflow is to work on a low poly mesh with an optimized topology for the needed animation's deformations and let the details be handled by the shader (via normal + height maps) and by some displacements with additional subdivisions when rendering.

As I just want to test your model for rigging, I used a decimate modifier in un-subdivide mode with an even iteration. The suit being a more complex organic part, I used Instant Meshes, it's certainly not the best solution but it a nice last hand option in my case.
Then I tried to use Rigify on it, and it went well. I had to do some weights assignments manually on some parts (especially the pockets and some parts of the helmet), but nothing fancy. So IMO you should work on obtaining animation ready models first.